British Pat. No. 135 549 discloses a cellular structure of this nature for heat exchange in a gas works. The various gases flow through concentric zones such that the heat exchange area between the gases is fairly small. Heat exchange takes place under rather unfavourable conditions and there remain high temperature differences between the inlet hot gas and the outlet heated gas and between the inlet cold gas and the outlet cooled gas.
Preferred embodiments of the present invention mitigate this drawback by providing an easily fabricated cylindrical cellular structure having a large area of contact per unit volume. Ease of fabrication is particularly desirable when the structure is made of ceramics material such as is required for operation at high temperatures, say in the range 1200.degree. C. to 1400.degree. C.